1. Field of the Invention
The present invention concerns a plane light source apparatus, a light guide plate and a display and more particularly a plane light source apparatus, a light guide plate and a display having a plurality of convexoconcave portions extending in the direction opposed to the light incident surface on a light emitting surface or on a surface opposed to the same of the light guide plate.
2. Detailed Description of the Prior Art
It is FIG. 8 and FIG. 9 that show an outline composition of a conventional plane light source. First, the plane light source 80 shown in FIG. 8 has a light source 81 substantially linear light source such as cold cathode fluorescent lamp, a light guide plate 82 made into plate-shape with transparence member such as acrylic resin, and a plurality of prism sheets 83 including fine ridge form prism structures 83a disposed closely, and formed into a sheet. A liquid crystal display panel 85 disposed in front of the plane light source 80 displays the image by controlling the penetration of the light emitted from the plane light source apparatus 80.
The cold cathode fluorescent lamp 81 is disposed in the plate thickness face of the light guide plate 82 and introduces the light inside this light guide plate 82. At this moment, a dot pattern 86 made of white paint printing or shallow round convexoconcave pattern is formed at the back of the light guide plate 82. The dot pattern 86 is disposed less dense in the vicinity of the cold cathode fluorescent lamp 81 and more dense the more distant from the cold cathode fluorescent lamp 81. This makes the brightness of the light emitted from a light emitting surface 87 approximately even.
Moreover, for instance, two of prism sheets 83 cover the light emitting surface 87 substantially orthogonal to the prism cut 83a, affording a convenient directivity to the diffused state light by the dot pattern 86, making the illumination brighter and improving further the light evenness.
Here, in recent years, according to the large-sizing of liquid crystal display panel 85, it is required to make the plane light source apparatus further lighter and thinner. At the same time, according to the diffusion of liquid crystal display apparatus, it is required to cut the cost all the more. The plane light source apparatus 90 shown in FIG. 9 is devised to meets these requirements.
And, in this conventional plane light source apparatus 90, which is including a liquid crystal display panel 95, a prism portion 97a wherein ridges similar to a prism structure portion 93a of a prism sheet 93 are provided in close contact is disposed on a light emitting surface 97 of a light guide plate 92, substantially orthogonal to the place where a light source is disposed. This intends to reduce the number of prism sheets 93 to be used.
Note that the plane light source apparatus using a light guide plate having a prism structure parallel to the linear light source is described, for example, in Japan Patent publication Hei 7-20466, or, Japan Patent publication Hei 8-254616. Also, the plane light source apparatus using a light guide plate having a prism structure extending in the direction vertical to the linear light source is described, for example, in Japan Patent publication Hei 7-301713. This Specification disclosed a light guide plate having a groove structure for diffused reflection of light, on a reflection surface opposed to the light emitting surface.
However, in a plane light source apparatus 90 shown in said FIG. 9, dark portions D are generated to the portions corresponding to both ends of the light source 91 as shown in FIG. 10, and this quality deterioration is notable for the plane light source apparatus 80 of the old composition. Such problem does not occur when the prism structure portion is formed in parallel to the light incident surface. Because, the prism structure portion, extending parallel to the linear light source axis, does not interfere with the light propagation to both ends. The first object of the present invention consists in providing a plane light source apparatus, a light guide plate and a display permitting to enhance the front brightness. Another object of the present invention consists in providing a plane light source apparatus, a light guide plate and a display permitting to reduce the number of components. Still another object of the present invention consists in providing a plane light source apparatus, a light guide plate and a display permitting to uniform the brightness in the plane.
The light guide plate according to the present invention has convexoconcave portions on the light emitting surface or on the surface opposed to the same. This convexoconcave portion extends in the direction opposed to the light incident surface of the light guide plate. Moreover, a flat face is formed at the bottom of the concave portion or at the top face of the convex portion. By providing such flat face, the light propagation to the side face of the light guide plate can be facilitated.
The light guide plate has a light incident surface where the light from a light source is introduced, a light emitting surface for emitting light from the light source, and an opposed surface opposed to the light emitting surface, the light emitting surface and the opposed surface extend in the direction opposed to the light incident surface, have a plurality of convexoconcave portions formed to collect substantially light propagating in said light guide plate, and the convexoconcave portions have a flat face formed at the bottom of the concave portion or at the top face of the convex portion.
The flat face is typically formed substantially vertical to the light incident surface or to a surface opposed to the light incident surface. And, the convexoconcave portions are preferably formed continuously with a pitch equal or inferior to 1 mm. Or, typically, the convexoconcave portions have a flat face at the bottom of the concave portion, and the breadth of the flat face is substantially identical to the breadth of the bottom surface portion of the convex portion. Besides, the area ratio of the flat face of said light emitting surface is formed to be larger at the center of the light emitting surface than at the end portion of the light emitting surface.
Taken as plane light source apparatus, the embodiment of the present invention is a plane light source apparatus having a lamp as light source and a light guide plate for directing and emitting the light from the lamp, and the light guide has a light incident surface opposed to the lamp and where the light from the lamp enters, a light emitting surface for emitting light from the lamp, and an opposed surface opposed to the light emitting surface, the light emitting surface and the opposed surface extend in the direction opposed to the light incident surface, have a plurality of convexoconcave portions formed to collect substantially light propagating in said light guide plate, and the convexoconcave portions have a flat face formed at the bottom of the concave portion or at the top face of the convex portion.
This plane light source apparatus can, further, include a prism sheet having a prism structure portion on the plane. This prism sheet is disposed preferably so that the prism surface is opposed to the light guide plate and the prism structure section crosses the convexoconcave portions on said light guide plate. Otherwise, it is preferable that the prism surface faces the opposite side of the light guide plate, and the prism structure portion is disposed to cross crosses the convexoconcave portions on said light guide plate. It is more preferable that the prism structure portion and said convexoconcave portions have a crossing angle (xcex1, xcex2) equal or superior to 45 degrees.
The plane light source apparatus, further, includes a first prism sheet and a second prism sheet having a prism structure on the surface, and the first and second prism sheets can be disposed so that the prism surface faces the opposite side of the light guide plate and the prism structure portion crosses the convexoconcave portions on the light guide plate. Preferably, the first prism sheet and the second prism sheet are disposed to cross.
The convexoconcave portions on the light guide plate are preferably provided with a flat face at all concave portions or all convex portions. Typically, the flat face is formed substantially vertical to the light incident surface or to the surface opposed to said light incident surface.
Taken as display apparatus, the embodiment of the present invention comprises a plane light source apparatus and a display panel for displaying image using the light from the linear light source apparatus, the linear light source apparatus has a light guide plate for directing and emitting the light from the light source, the light guide plate includes a light incident surface where the light from the light source enters, a light emitting surface, and an opposed surface opposed to the light emitting surface, the light emitting surface or the opposed surface includes a plurality of convexoconcave portions extending in the direction opposed to the light incident surface and formed to substantially collect the light propagating in the light guide plate, and the convexoconcave portions have a flat face formed at the bottom of the concave portion or at the top face of the convex portion. Typically, the flat face is formed substantially parallel to the display surface of said display panel. Preferably, the convexoconcave portions have a pitch smaller than the auxiliary pixel portion pitch of said display panel.